NEW YORK (CNN) -- Disgraced track star Marion Jones has returned her Olympic medals after pleading guilty to a charge of lying to federal agents about her use of steroids, anti-doping regulators and her attorney said Monday.

Jones, 31, won three gold and two bronze medals at the 2000 Olympic games in Sydney, Australia. But Friday, after years of public and often angry denials, she admitted that she used the steroid THG, known as "the clear," from 1999 to 2001.

Jones' admission that she lied to federal investigators probing the use of performance-enhancing drugs in sports means she faces possible prison time. She has been ordered back to court on January 11 for sentencing.

"It is with a great amount of shame that I stand before you and tell you I have betrayed your trust," she said after Friday's hearing.

On Monday, the U.S. Anti-Doping Agency announced she has been declared ineligible for competition for two years and has relinquished her medals. Her lawyer, S. Hill Allen, said he did not know where or to whom the medals were handed over.

The admission by the woman frequently called one of the greatest female athletes of her time could also have ripple effects throughout the sports world, particularly for the investigation into alleged doping by other high-profile athletes.

Jones' admission is part of the four-year-old probe of Bay Area Laboratory Cooperative, or BALCO, which produced "the clear" -- an undetectable designer steroid. The performance-enhancing substance gives athletes an edge in strength and endurance, and allows muscles to recover quickly from heavy workouts and competition.

She was one of numerous prominent athletes who appeared before a federal grand jury in San Francisco as part of the case; others included baseball home-run title-holder Barry Bonds and New York Yankees slugger Jason Giambi.

In 2004, Jones filed a $25 million defamation lawsuit against BALCO owner Victor Conte, accusing him of trying to "destroy her career and reputation" when he said he had supplied her with performance-enhancing drugs. The case was settled out of court for an undisclosed amount, and Conte pleaded guilty to money laundering and conspiracy to distribute steroids in 2005.

It wasn't immediately clear what will happen next with previous results.

The International Olympic Committee and other sports bodies can go back eight years to strip medals and nullify results, according to The Associated Press. In Jones' case, that would include the 2000 Olympics, where she won gold in the 100 meters, 200 meters and 1,600 relay and bronze in the long jump and 400 relay.

The standings normally would be readjusted, with the second-place finisher moving up to gold, third to silver and fourth to bronze, according to the AP.

Pauline Davis-Thompson of the Bahamas was the silver medalist in the 200 meters, and Tatiana Kotova of Russia was fourth in the long jump.

The silver medalist in the 100 meters in Sydney was Greek sprinter Katerina Thanou -- at the center of a major doping scandal at the Athens Olympics. She and fellow Greek runner Kostas Kenteris failed to show up for drug tests on the eve of the games, claimed they were injured in a motorcycle accident and eventually pulled out. Both later were suspended for two years.